Effect of Defects on Structural Integrity in High-Heat-Input Weldment

Abstract

With the rapid increase in the size of container ships, the steel plates used for ship hulls have increased in thickness. The use of thick plates leads to an increase in welding. Alternative welding processes such as electro gas welding (EGW), with high heat input have been replacing the multi-pass flux cored arc welding process. Shipbuilding companies have tended to use EGW increasingly to improve productivity. However, because the toughness of steel tends to decrease for thicker plates, brittle fracture requireded more attention. Although some research on high-heat-input EGW weld joints has been performed, much less attention has been paid to estimating the integrity of defective high-heat-input weld joints. The purpose of this study was to determine the reliability of EGW weld joints for thick plates. To do so, the fracture toughness of EGW weld joints was investigated. In addition, to estimate the integrity of defective welds, the fatigue characteristics of experimentally reproduced defective welds were examined. Based on these investigations, an engineering critical assessmentwas conducted. As a result, a standard for the allowable defect size for field application according to the defect type is proposed.